Ultrasound catheter having protective feature against breakage

ABSTRACT

An ultrasound catheter has an elongate flexible catheter body having a lumen extending longitudinally therethrough, and an ultrasound transmission member extending longitudinally through the lumen of the catheter body. The ultrasound transmission member has a proximal end that is coupled to a separate ultrasound generating device, and a distal end that terminates at the distal end of the catheter body, with at least a portion of the distal end of the ultrasound transmission member extending outside the lumen of the catheter body and beyond the distal end of the catheter body, and with the ultrasound transmission member directly attached to the catheter body via an attachment device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.11/594,663, filed Nov. 7, 2006, entitled “ULTRASOUND CATHETER HAVINGPROTECTIVE FEATURES AGAINST BREAKAGE,” which is hereby incorporated byreference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention pertains to medical equipment, and moreparticularly, to a therapeutic ultrasound system for ablatingobstructions within tubular anatomical structures such as blood vessels.The ultrasound system includes a protective feature that minimizes theintroduction of debris into the patient's vasculature if the ultrasoundtransmission member were to break, fracture or become dislodged during amedical procedure.

2. Description of the Related Art

A number of ultrasound systems and devices have heretofore been proposedfor use in ablating or removing obstructive material from blood vessels.Ultrasound catheters have been utilized to ablate various types ofobstructions from blood vessels of humans and animals. Successfulapplications of ultrasound energy to smaller blood vessels, such as thecoronary arteries, requires the use of relatively small diameterultrasound catheters which are sufficiently small and flexible toundergo transluminal advancement through the tortuous vasculature of theaortic arch and coronary tree. However, because of its small diameter,the ultrasound transmission member which extends through such cathetersis particularly susceptible to losses in the transmitted ultrasoundenergy, and breakage.

Breakage of ultrasound transmission members often occurs near theproximal end thereof, generally at the coupling between the ultrasoundcatheter coupling and the ultrasound transducer. This is believed to bebecause energy concentrations and stresses are highest at these points.Thus, any external forces applied to the ultrasound transmission memberin this region may result in stresses exceeding the elastic limit of theultrasound transmission member.

External forces may be inadvertently and undesirably applied to theultrasound transmission member by pressing upon, pushing, pulling,torquing, bending or bumping the ultrasound transmission member couplingduring use of the ultrasound catheter. Such forces when applied to theultrasound catheter coupling area further result in limited ultrasoundenergy transmission through the ultrasound transmission member. Ifultrasound energy is being transmitted by the ultrasound transmissionmember at the instant such forces are applied thereto, additionalstresses occur which may result in breakage of the ultrasoundtransmission member.

Breakage of ultrasound transmission members can also occur near thedistal end thereof, generally at the area of the smallest cross-section.Therefore, it is important that any debris resulting from the breakageof the ultrasound transmission member not be allowed to be introducedinto a patient's vasculature during a medical procedure.

Thus, there still exists a need to protect against breakage of theultrasound transmission member during a medical procedure.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an ultrasoundcatheter system with a protective feature that prevents or minimizes theintroduction of debris into the patient's vasculature if the ultrasoundtransmission member were to break or fracture during a medicalprocedure.

In order to accomplish the objects of the present invention, there isprovided an ultrasound catheter having an elongate flexible catheterbody having a lumen extending longitudinally therethrough, and anultrasound transmission member extending longitudinally through thelumen of the catheter body. The ultrasound transmission member has aproximal end that is coupled to a separate ultrasound generating device,and a distal end that terminates at the distal end of the catheter body,with at least a portion of the distal end of the ultrasound transmissionmember extending outside the lumen of the catheter body and beyond thedistal end of the catheter body, and with the ultrasound transmissionmember directly attached to the catheter body via an attachment device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an ultrasound system according to thepresent invention.

FIG. 2 is a cross-sectional view of the distal end of an ultrasoundcatheter that can be used with the system of FIG. 1 according to oneembodiment thereof.

FIG. 3 is a side sectional view of an ultrasound transmission memberthat can be used with the system of FIG. 1.

FIGS. 4-9 are cross-sectional views of the distal end of variousultrasound catheters that can be used with the system of FIG. 1according to different embodiments thereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The following detailed description is of the best presently contemplatedmodes of carrying out the invention. This description is not to be takenin a limiting sense, but is made merely for the purpose of illustratinggeneral principles of embodiments of the invention. The scope of theinvention is best defined by the appended claims. In certain instances,detailed descriptions of well-known devices, compositions, components,mechanisms and methods are omitted so as to not obscure the descriptionof the present invention with unnecessary detail.

FIG. 1 illustrates an ultrasound system according to the presentinvention for use in ablating and removing occlusive material inside thevessel of an animal or human. Referring to FIGS. 1 and 2, the ultrasoundsystem includes an ultrasound catheter device 10 which has an elongatecatheter body 11 having a proximal end 12, a distal end 14, and definingat least one lumen 15 extending longitudinally therethrough. Theultrasound catheter device 10 is operatively coupled at its proximal end12, by way of a Y-connector 18, a catheter knob 20, and a slide collar22, to an ultrasound transducer 24. The ultrasound transducer 24 isconnected to a signal generator 26, which can be provided with a footactuated on-off switch 28. The signal generator 26 can be supported byan IV pole 27. When the on-off switch 28 is depressed, the signalgenerator 26 sends an electrical signal to the ultrasound transducer 24,which converts the electrical signal to ultrasound energy. Suchultrasound energy subsequently passes through the catheter device 10 andis delivered to the distal end 14. A guidewire 25 may be utilized inconjunction with the catheter device 10, as will be more fully describedbelow.

The catheter body 11 is formed of a flexible polymeric material such asnylon (Pebax™) manufactured by Atochimie, Cour be Voie, Hauts Ve-Sine,France. The flexible catheter body 11 is preferably in the form of anelongate tube having one or more lumens extending longitudinallytherethrough. The catheter body 11 defines a main lumen 15. Extendinglongitudinally through the main lumen 15 is an elongate ultrasoundtransmission member 16 having a proximal end which is removablyconnectable to the ultrasound transducer 24 via a sonic connector (notshown) such that ultrasound energy will pass through the ultrasoundtransmission member 16. As such, when the foot actuated on-off switch 28operatively connected to the ultrasound transducer 24 is depressed,ultrasound energy will pass through the ultrasound transmission member16 to the distal end 14 of the catheter body 11.

A guidewire port 58 is provided in the catheter body 11 at any locationalong the catheter body 11. A guidewire lumen 60 extends from theguidewire port 58 through the main lumen 15 of the catheter body 11 in amanner that is concomitant to the length of the ultrasound transmissionmember 16. In one embodiment, the guidewire port 58 can be provided at alocation that is closer to the proximal end 12 than to the distal end 14of the catheter.

In one embodiment, the ultrasound transmission member 16 may be formedof any material capable of effectively transmitting the ultrasonicenergy from the ultrasound transducer 24 to the distal end 14 of theultrasound transmission member 16, and is preferably made from metal ormetal alloys. It is possible to form all or a portion of the ultrasoundtransmission member 16 with one or more materials which exhibitsuper-elasticity. Such materials should preferably exhibitsuper-elasticity consistently within the range of temperatures normallyencountered by the ultrasound transmission member 16 during operation ofthe catheter device 10. Specifically, all or part of the ultrasoundtransmission member 16 may be formed of one or more metal alloys knownas “shape memory alloys.”

Examples of super-elastic metal alloys which are usable to form theultrasound transmission member 16 of the present invention are describedin detail in U.S. Pat. No. 4,665,906 (Jervis); U.S. Pat. No. 4,565,589(Harrison); U.S. Pat. No. 4,505,767 (Quin); and U.S. Pat. No. 4,337,090(Harrison). The disclosures of U.S. Pat. Nos. 4,665,906; 4,565,589;4,505,767; and 4,337,090 are expressly incorporated herein by referenceinsofar as they describe the compositions, properties, chemistries, andbehavior of specific metal alloys which are super-elastic within thetemperature range at which the ultrasound transmission member 16 of thepresent invention operates, any and all of which super-elastic metalalloys may be usable to form the super-elastic ultrasound transmissionmember 16.

The frontal portion of the Y-connector 18 is connected to the proximalend 12 of the catheter 10 using techniques that are well-known in thecatheter art. An injection pump 54 or IV bag (not shown) or syringe (notshown) can be connected, by way of an infusion tube 55, to an infusionport or sidearm 72 of the Y-connector 18 (see FIG. 1). The injectionpump can be used to infuse coolant fluid into and/or through the mainlumen 15 of the catheter 10, with the coolant fluid exiting viairrigation outlets 32 (see FIG. 2) provided adjacent the distal end 14of the catheter 10. Such flow of coolant fluid may be utilized toprevent overheating of the ultrasound transmission member 16 extendinglongitudinally through the main lumen 15. Such flow of the coolant fluidthrough the main lumen 15 of the catheter 10 also serves to bathe theouter surface of the ultrasound transmission member 16, therebyproviding for an equilibration of temperature between the coolant fluidand the ultrasound transmission member 16. Thus, the temperature and/orflow rate of coolant fluid may be adjusted to provide adequate coolingand/or other temperature control of the ultrasound transmission member16. The irrigation fluid can include a pharmacological agent and/ormicrobubbles.

In addition to the foregoing, the injection pump 54 or syringe may beutilized to infuse a radiographic contrast medium into the catheter 10for purposes of imaging. Examples of iodinated radiographic contrastmedia which may be selectively infused into the catheter 10 via theinjection pump 54 are commercially available as Angiovist 370 fromBerlex Labs, Wayne, N.J. and Hexabrix from Malinkrodt, St. Louis, Mo.

The proximal end of the Y-connector 18 is attached to the distal end ofthe catheter knob 20 by threadably engaging the proximal end of theY-connector 18 inside a threaded distal bore (not shown) at the distalend of the catheter knob 20.

The proximal end of the ultrasound transmission member 16 is attached toa sonic connector (not shown) which is configured to effect operativeand removable attachment of the proximal end of the ultrasoundtransmission member 16 to the horn of the ultrasound transducer 24. Thesonic connector is preferably configured and constructed to permitpassage of ultrasound energy through the ultrasound transmission member16 with minimal lateral side-to-side movement of the ultrasoundtransmission member 16 while, at the same time, permitting unrestrictedlongitudinal forward/backward vibration or movement of the ultrasoundtransmission member 16. Examples of ultrasound transducers, sonicconnectors and their connections are illustrated in U.S. Pat. Nos.6,702,748, 6,855,123, 6,942,620 and 6,942,677, whose disclosures areincorporated by this reference as though set forth fully herein.

Referring to FIGS. 2 and 3, the ultrasound transmission member 16 canhave progressively tapered regions extending from the proximal end 34thereof to the distal tip 36 thereof. For example, the proximal-mostregion 38 can have a constant diameter which is the greatest diameteralong the length of the ultrasound transmission member 16. The region 38transitions at its distal end to a first tapered region 40 whichgradually decreases in diameter to its distal end to a second taperedregion 42, which gradually decreases in diameter to its distal end to athird tapered region 44, which gradually decreases in diameter to itsdistal end to the distal tip 36. Each tapered region 40, 42, 44 can havea continuous taper, and be tapered to different degrees, such that theregion 40 has a greater taper than the region 42, which in turn has agreater taper than the region 44. The distal-most part of the region 44can have the smallest diameter along the entire ultrasound transmissionmember 16. The continuously decreasing tapering from the proximal to thedistal direction shown in FIG. 3 allows for improved ultrasound energypropagation. The distal tip 36 can have a proximal section 46 whichgradually increases in diameter until it reaches the proximal end of adistal section 48. The distal section 48 can have a bulbousconfiguration having a rounded or curved distal-most end that is adaptedto contact the obstruction for ablation thereof. Thus, the distal tip 36can have an enlarged size when compared to the rest of the ultrasoundtransmission member 16 so that the distal tip 36 can function as thedistal head for the catheter 10.

In the embodiment shown in FIG. 2, the distal end 14 of the catheterbody 11 has an opening 30, and the distal tip 36 of the ultrasoundtransmission member 16 is secured to the inner wall 62 of the main lumen15 of the catheter body 11 adjacent the opening 30. The securement canbe accomplished by an attachment mechanism 64 (which can be glue,welding or fusing) at the location of the proximal section 46 and theinner wall 62, so that part of the proximal section 46 is receivedinside the main lumen 15 and with the distal section 48 of the distaltip 36 extending outside the main lumen 15 of the catheter body 11. Theopening 30 of the catheter body 11 is closed by the connection of thedistal tip 36 to the catheter body 11. The construction shown in FIG. 2directly attaches the ultrasound transmission member 16 to the catheterbody 11 (via the attachment mechanism 64), which provides additionalprotection if the ultrasound transmission member 16 experiencesbreakage. In particular, if the ultrasound transmission member 16fractures, breaks or splinters, the distal tip 36 will still remainsecured to the catheter body 11 via the attachment device 64, and willnot become dislodged from the catheter body 11. Thus, the embodiment ofFIG. 2 does not employ a separate distal head for the catheter 10, butinstead utilizes the distal tip 36 of the ultrasound transmission member16 as a distal head which is secured directly to the distal end of thecatheter body 11.

FIGS. 4-5 illustrate two different embodiments of a distal end of thecatheter 10 which utilize the same principles and general constructionas in FIG. 2, except that a distal cap is secured to the distal tip ofthe ultrasound transmission member. Therefore, the same numeraldesignations are used in FIGS. 2, 4 and 5 to designate the same orsimilar elements, except that an “a” and a “b” are added to the numeraldesignations in FIGS. 4 and 5, respectively. The differences between theembodiment of FIG. 2 and the embodiments in FIGS. 4 and 5 are describedbelow.

The distal end 14 a in FIG. 4 differs from the distal end 14 in FIG. 2in that a protective cap 66 a is secured to the distal section 48 a ofthe distal tip 36 a of the ultrasound transmission member 16 a. The cap66 a can function as the tip of the catheter 10. The distal tip 36 aitself has a different configuration from the distal tip 36 in FIG. 2 inthat the distal section 48 a is not bulbous or curved, but instead has aconstant diameter that terminates distally at a flat distal end 68 a.The cap 66 a has a cylindrical configuration with an opened proximal endand a curved or bulbous distal end 70 a. The distal section 48 a of thedistal tip 36 a is received into the hollow bore 72 a of the cap 66 avia the opened proximal end of the cap 66 a, and is secured to the cap66 a inside the bore 72 a via an attachment device 74 a (which can bethe same as the attachment device 64). The cap 66 a can be made of aradiopaque material to improve the visibility of the distal tip 36 a.

In addition, instead of the attachment mechanism 64, the embodiments ofFIGS. 4-5 provide an intermediate member 64 a. The intermediate member64 a can be a cylindrical component that is positioned around theultrasound transmission member 16 a, and between the ultrasoundtransmission member 16 a and the inner wall 62 a of the catheter body 11a. The intermediate member 64 a (as well as 64 and 64 b) is preferablymade from a material that does not effectively transfer or conduct heat,and which is easy to attach to the ultrasound transmission member 16 aand the catheter body 11 a. Examples of the material can include certainepoxies, polymers, plastics and rubber. According to one embodiment, theintermediate member 64 a can be fused to the ultrasound transmissionmember 16 a and the inner wall 62 a. According to another embodiment,the intermediate member 64 a can be bonded to the ultrasoundtransmission member 16 a and the inner wall 62 a. According to yetanother embodiment, the intermediate member 64 a can be fused to theultrasound transmission member 16 a and bonded to the inner wall 62 a.The intermediate member 64 a serves as a safety feature to hold theultrasound transmission member 64 a within the catheter body 11 in theevent the ultrasound transmission member 16 a experiences breakage at alocation proximal to the intermediate member 64 a. However, theintermediate member 64 a will not be able to hold the distal tip 36 a ifthe breakage occurs at the distal tip 36 a.

The distal end 14 b in FIG. 5 differs from the distal end 14 a in FIG. 4in the following ways. First, the guidewire port 58 a, guidewire 25 a,and guidewire lumen 60 a have been omitted. Second, the distal tip 36 bitself has a different configuration from the distal tip 36 a in FIG. 4in that a distal extension 76 b extends distally from the distal section48 b. The distal extension 76 b has a smaller constant diameter than thediameter of the enlarged distal section 48 b, and the distal extension76 b is received into the hollow bore 72 b of the cap 66 b via theopened proximal end of the cap 66 b, and is secured to the cap 66 binside the bore 72 b via an attachment mechanism 74 b (which can be thesame as the attachment mechanism 64). The cap 66 b can also be made of aradiopaque material to improve the visibility of the distal tip 36 b.

Third, the intermediate member 64 b in FIG. 5 has a differentconfiguration as the intermediate member 64 a. The intermediate member64 b has a generally conical configuration, having a wider diameter atits distal end 78 b (which resembles the base of the cone) and anarrower diameter or dimension at its proximal end 80 b (which resemblesthe narrowed tip of a cone). The hollow interior 82 b of theintermediate member 64 b has the greatest inner diameter adjacent itsdistal end 78 b and decreases to its smallest inner diameter adjacentthe proximal end 80 b. This configuration for the intermediate member 64b allows the ultrasound transmission member 16 b to be fitted andretained inside the hollow interior 82 b without the need to directlyattach the ultrasound transmission member 16 b to the intermediatemember 64 b. Specifically, the sections 46 b, 48 b can be retainedinside the hollow interior 82 b, with the transition between the region44 b and the distal tip 36 b (i.e., where the diameter of the ultrasoundtransmission member 16 b is the smallest) received in the narrow openingof the proximal end 80 b of the intermediate member 64 b. In otherwords, the proximal end 80 b overlaps a dimensional step (i.e., thetransition between the region 44 b and the distal tip 36 b) on theultrasound transmission member 16 b. The distal extension 76 b extendsthrough another opening at the distal end 78 b of the intermediatemember 64 b. To provide additional protection or safety, any or all ofthe sections 46 b, 48 b can also be bonded to the inner wall of theintermediate member 64 b. The outer surface 84 b of the intermediatemember 64 b may be attached to the opened distal end of the catheterbody 11 b by bonding, fusing or glue, and part of the intermediatemember 64 b extends beyond the distal end of the catheter body 11 b.

Comparing the embodiments of FIGS. 4 and 5, the intermediate member 64 bhas an “overlapped” configuration, which provides added protectionbecause the intermediate member 64 b is seated on a dimensional stepalong the ultrasound transmission member 16 b, and will always hold theproximal portions of the ultrasound transmission member 16 b within thecatheter body 11 b as long as the intermediate member 64 b is attachedto the catheter body 11 b.

FIG. 6 illustrates a modification that can be made to the embodiment inFIG. 4. The embodiments in FIGS. 4 and 6 utilize the same principles andgeneral construction, so the same numeral designations are used in FIGS.4 and 6 to designate the same or similar elements, except that a “c” isadded to the numeral designations in FIG. 6.

In FIG. 6, the catheter body 11 c, the guidewire port 58 c, theguidewire lumen 60 c, the guidewire 25 c, the ultrasound transmissionmember 16 c and the cap 66 c can be the same as the catheter body 11 a,the guidewire port 58 a, the guidewire lumen 60 a, the guidewire 25 a,the ultrasound transmission member 16 a and the cap 66 a in FIG. 4. Theprimary difference is that the intermediate member 64 a is now embodiedin the form of an anchor wire 64 c, which can be either a polymer or ametal. One end 86 c of the wire 64 c can be attached (e.g., by glue,fusing, bonding) to the inner wall 62 c of the catheter body 11 c, andthe other end 88 c of the wire 64 c can be attached (e.g., by glue,bonding or welding) to the distal tip 36 c and to the cap 66 c. If theultrasound transmission member 16 c breaks at any location, then theultrasound transmission member 16 c will be retained inside the catheterbody 11 c.

FIG. 7 illustrates a modification that can be made to the embodiment inFIG. 6. Specifically, the embodiments in FIGS. 6 and 7 are the sameexcept that the guidewire port 58 c, the guidewire lumen 60 c and theguidewire 25 c are omitted in FIG. 7, and the anchor wire 64 d isattached to the distal end of the ultrasound transmission member 16 dbut not attached to the cap 66 d. Therefore, the same numeraldesignations are used in FIGS. 6 and 7 to designate the same elements,except that a “d” is added to the numeral designations in FIG. 7, and nofurther description of the elements in FIG. 7 is needed.

Attaching the anchor wire 64 c or 64 d to the cap 66 c or 66 d, or notattaching the anchor wire 64 c or 64 d to the cap 66 c or 66 d, providesdifferent options. Attaching the anchor wire 64 c to the cap 66 cprevents dislodgement of the cap 66 c or the distal tip 36 c if thebreakage occurs near or at the distal tip 36 c. However, breakage atsuch locations is rare, so the embodiment in FIG. 7 (where the anchorwire 64 d is not attached to the cap 66 d) can also be employed.

FIG. 8 illustrates another modification that can be made to theembodiment in FIG. 4. Specifically, the embodiments in FIGS. 4 and 8 arethe same, except that the proximal portion of the cap 66 e has anannular edge 67 e that extends into the interior of the catheter body 11e. Therefore, the same numeral designations are used in FIGS. 4 and 8 todesignate the same elements, except that an “e” is added to the numeraldesignations in FIG. 8, and no further description of the elements inFIG. 8 is needed. The annular edge 67 e is not attached to the catheterbody 11 e, and is maintained separate from the catheter body 11 e. Onebenefit which is provided by extending a portion of the cap 66 e intothe catheter body 11 e is that this arrangement provides a smooth andfriendly transition between the distal cap 66 e and the catheter body 11e. This smooth transition facilitates navigation of the distal end 14 ethrough tortuous anatomy. Also, the non-affixed tip of the catheter body11 e can result in the improved transmission of ultrasound energy fromthe transducer to the distal end 14 e.

FIG. 9 illustrates a modification that can be made to the embodiment inFIG. 5. Specifically, the embodiments in FIGS. 5 and 9 are the sameexcept that the intermediate member 64 f is completely retained insidethe catheter body 11 f and the proximal portion of the cap 66 f has anannular edge 67 f that extends into the interior of the catheter body 11f. Therefore, the same numeral designations are used in FIGS. 5 and 9 todesignate the same elements, except that an “f” is added to the numeraldesignations in FIG. 9, and no further description of the elements inFIG. 9 is needed.

A guidewire has been included in the embodiments of FIGS. 2, 4, 6 and 8,while the guidewire has been omitted in the embodiments of FIGS. 5, 7and 9. Embodiments showing the use or omission of a guidewire are shownfor reference only. The principles of the present invention may beapplied to catheters that include, or not include, a guidewire. The useor omission of a guidewire depends upon the choice of the clinician, andis often dictated by the access difficulty or specific clinicalsituations. For example, if the target lesion is located on a straightportion of the vessel, use of a non-guidewire embodiment will befeasible and relatively easy. On the other hand, if the target lesion islocated in a tortuous location of the vessel, then use of a guidewireembodiment will help the clinician to navigate the distal tip 36 to thelocation of the lesion.

While the description above refers to particular embodiments of thepresent invention, it will be understood that many modifications may bemade without departing from the spirit thereof. The accompanying claimsare intended to cover such modifications as would fall within the truescope and spirit of the present invention.

1. A method of ablating tissue in a vessel, comprising: providing anultrasound catheter comprising an elongate flexible catheter body havinga proximal end, a distal end, and a lumen extending longitudinallytherethrough, and an ultrasound transmission member extendinglongitudinally through the lumen of the catheter body, the ultrasoundtransmission member having a proximal end and a distal end, at least aportion of the distal end of the ultrasound transmission memberextending beyond the distal end of the catheter body, the ultrasoundtransmission member being irremovably attached to the catheter body; andcausing the distal end of the ultrasound transmission member to contactthe tissue.
 2. The method of claim 1 further comprising providing anintermediate member disposed between and attached to the ultrasoundtransmission member and the catheter body.
 3. The method of claim 2,wherein the intermediate member is disposed on a proximal side of thedistal end of the ultrasound transmission member.
 4. The method of claim2, wherein the intermediate member extends beyond the distal end of thecatheter body.
 5. The method of claim 2, wherein the intermediate memberforms a continuous cross-section between at least a portion of theultrasound transmission member and at least a portion of the catheterbody so as to inhibit longitudinal movement of the ultrasoundtransmission member relative to the catheter body.
 6. The method ofclaim 1 further comprising radiographically imaging the distal end ofthe ultrasound transmission member.
 7. The method of claim 1 furthercomprising advancing the ultrasound catheter within the vessel and overa guidewire.
 8. The method of claim 1 further comprising flowing a fluidwithin the lumen of the catheter body over at least a portion of theultrasound transmission member.
 9. The method of claim 8, wherein thefluid comprises a radiographic contrast media.
 10. The method of claim1, wherein causing the distal end of the ultrasound transmission memberto contact the tissue comprises directly contacting the tissue with theultrasound transmission member.
 11. The method of claim 1, wherein theultrasound catheter comprises a cap secured to the distal end of theultrasound transmission member.
 12. The method of claim 11, whereincausing the distal end of the ultrasound transmission member to contactthe tissue comprises directly contacting the tissue with the cap. 13.The method of claim 11, wherein the ultrasound catheter comprises anattachment member positioned between and attached to the ultrasoundtransmission member and the cap.
 14. A method comprising: providing anultrasound catheter comprising a body having a proximal end, a distalend, and at least one lumen extending longitudinally therethrough, anultrasound transmission member disposed in the at least one lumen of thebody and having a proximal end and a distal end, an intermediate membercoupling the ultrasound transmission member to the body and beingdisposed on a proximal side of the distal end of the ultrasoundtransmission member; and transmitting ultrasonic energy through at leasta portion of the ultrasound transmission member.
 15. The method of claim14, wherein a cross-section through the intermediate member iscontinuous between at least a portion of the ultrasound transmissionmember and at least a portion of the body.
 16. The method of claim 14further comprising contacting tissue within a vessel with the distal endof the ultrasound transmission member.
 17. A method comprising:providing an ultrasound catheter comprising a body having a proximalend, a distal end, and at least one lumen extending longitudinallytherethrough, an ultrasound transmission member disposed in the lumen ofthe body and having a proximal end and a distal end, and an intermediatemember attached to the ultrasound transmission member and the body so asto inhibit longitudinal movement of the ultrasound transmission memberrelative to the body, the intermediate member being disposed between thedistal and proximal ends of the body; and introducing the ultrasoundcatheter into a patient's vasculature.
 18. The method of claim 17further comprising transmitting ultrasound energy through at least aportion of the ultrasound member.
 19. The method of claim 17, whereinthe intermediate member forms a continuous cross-section between atleast a portion of the ultrasound transmission member and at least aportion of the catheter body.
 20. The method of claim 17, wherein aportion of the ultrasound transmission member disposed on a distal sideof the intermediate member comprises a radiographic material.